Background This paper describes a randomised controlled trial (RCT) protocol aimed at investigating the efficacy of caregivers’ Mind-Mindedness training as an early intervention for preschoolers with social anxiety. Mind-mindedness, a caregiver's ability to recognise and respond to a child as an individual with their own thoughts, feelings, and intentions, is associated with secure attachment and socioemotional skills. While previous studies indicate brief Mind-Mindedness training may increase caregiver mentalisation in high-risk groups, rigorous research on the impacts of social anxiety in children is limited. Building on the well-established link between caregiver’s Mind-Mindedness and positive socioemotional outcomes in children, this study aims to bridge the existing research gap by directly testing the impact of Mind-Mindedness training on social anxiety. Methods This randomized controlled trial aims to recruit 100 caregivers of preschool-aged 4 to 7-year-old children with social anxiety from the UK and Iran. The caregivers will be randomly assigned to either a mind-mindedness training group (n=50) or a peer support (control) group(n=50). The mind-mindedness training will involve three online sessions focused on teaching strategies for using mind-minded comments, the program will consist of three online sessions, each lasting one hour and conducted over three consecutive weeks. The peer support (control) group will have access to a private online peer-support platform for sharing experiences. Measures of mind-mindedness, child social anxiety, attachment, and theory of mind will be assessed at baseline, post-intervention, and 3-month follow-up using established assessment tools. Discussion The study aims to evaluate the effectiveness of a mind-mindedness parental intervention for social anxiety in children and to uncover the potential mediating roles of attachment and theory of mind in the relationship between mind-mindedness and child anxiety. The cross-cultural design, involving participants from the UK and Iran, will offer valuable information on the cultural aspect of the intervention. The training group is hypothesized to lead to increased mind-mindedness and reduced child social anxiety versus a peer support (control) group. This research can establish evidence for mind-mindedness training as an early intervention approach for childhood social anxiety. Trial registration Prospectively registered on ClinicalTrials.gov (ID:NCT06657014; registered on 23th October 2024).